The water intake profile data are required for managing waterflooding process and, therefore, improvement of oil recovery factor. Determining a water intake profile means determining a relative proportion of the injected water which enters different intake zones. A combination of all intake zones forms a water intake interval of a well which had been perforated and penetrates within an oil and gas formation.
The most widespread method for determining a water intake profile in injection wells is a continuous flow meter logging during fluid injection (see, for example, Ipatov A. I., Kremenetsky M. I. “Geophysical and hydrodynamic methods of hydrocarbon field development monitoring”, Moscow, 2005, p. 108). Usually, mechanical flowmeters are used for this purpose. This method has such shortcomings as limitations imposed by well architecture, whereby logging is not always possible in an operating injection well.
There are other known methods for determining a water intake profile, such as radioisotope method, neutron logging, etc. As a rule, all these methods are complicated, expensive and are used rarely.
The first method for identifying water intake zones in injection wells was temperature survey after shutting down water injection (Nowak, T. J., 1953. The estimation of water injection profiles from temperature surveys. Petroleum transactions, Vol. 198, pp. 203-212).
It has been shown that temperature within water intake zones in a shut-in well relaxes significantly slower than temperatures above and below the water intake zones. Today, this method is widely used for determining water-intake zones boundaries.
Another known method for determining a water intake profile has been described in U.S. Pat. No. 8,146,656. This method involves shutting down water injection, repeated injection once water temperature in the well above a water-intake zone has increased due to heat exchange with surrounding rocks, and temperature monitoring during heated water moving along a water intake interval. According to this method, temperature front movements are used as a basis for determining a rate of water movement and, therefore, for determining water intake profile in the water intake zone.
One disadvantage of this invention is a low accuracy of determining the water intake profile caused by temperature front becoming too dispersed as it moves along the water intake interval. It is especially true for horizontal wells where length of water intake intervals can be 300-500 m and even more.